linux-kernel - Re: [PATCH v5 06/27] irq_domain/powerpc: eliminate irq_map; use irq_alloc

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Date:	Mon, 2 Apr 2012 22:55:24 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Grant Likely <grant.likely@...retlab.ca>
Cc:	Andreas Schwab <schwab@...ux-m68k.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	devicetree-discuss@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	Milton Miller <miltonm@....com>,
	Rob Herring <rob.herring@...xeda.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	linuxppc-dev@...ts.ozlabs.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v5 06/27] irq_domain/powerpc: eliminate irq_map; use
	irq_alloc_desc() instead

On Mon, Apr 02, 2012 at 02:28:48PM -0600, Grant Likely wrote:
> On Mon, 02 Apr 2012 18:29:15 +0200, Andreas Schwab <schwab@...ux-m68k.org> wrote:
> > Andreas Schwab <schwab@...ux-m68k.org> writes:
> > 
> > > Grant Likely <grant.likely@...retlab.ca> writes:
> > >
> > >> This patch drops the powerpc-specific irq_map table and replaces it with
> > >> directly using the irq_alloc_desc()/irq_free_desc() interfaces for allocating
> > >> and freeing irq_desc structures.
> > >
> > > This breaks irqs on PowerMac G5.  I see lost irq errors from the sata
> > > driver.
> > 
> > When I revert a09b659cd68c10ec6a30cb91ebd2c327fcd5bfe5 ("genirq: Fix
> > long-term regression in genirq irq_set_irq_type() handling") on top of
> > 3.4-rc1 the sata irq errors disappear, but I see a lot of spurious
> > interrupts.  Also the X server is broken somehow, though I don't know
> > whether that is related or a different bug.
> 
> That change is:
> 
> @@ -61,8 +61,7 @@ int irq_set_irq_type(unsigned int irq, unsigned int type)
>                 return -EINVAL;
>  
>         type &= IRQ_TYPE_SENSE_MASK;
> -       if (type != IRQ_TYPE_NONE)
> -               ret = __irq_set_trigger(desc, irq, type);
> +       ret = __irq_set_trigger(desc, irq, type);
>         irq_put_desc_busunlock(desc, flags);
>         return ret;
> 
> So presumably irq_set_irq_type() is getting called with type ==
> IRQ_TYPE_NONE.  From Russell's description, presumably that would mean
> the G5 sata driver isn't setting the correct type for the interrupt,
> but I have *no* idea how that intersects with the change removing the
> powerpc irq map.

Well, presumably someone is calling irq_set_irq_type() asking explicitly
for IRQ_TYPE_NONE.  The code will now (as it always used to before David's
change) do exactly what you ask this to: it will ask the type to be set
to none.

If you don't want to set the type to none, don't call the interface asking
for that to happen.
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